The compromise last year of the personal information of millions of current and former federal employees was entirely preventable, if the U.S. Office of Personnel Management that was attacked had taken the right measures on knowing it was targeted, according to a report set to be released Wednesday by the House Committee on Oversight and Government Reform.

“In our report, we are going to show that once we knew that this was happening, we didn’t make the right moves,” said Jason Chaffetz, chairman of the committee in an interview to CNN.

Saying that he thinks that the attack came from overseas, Chaffetz, a Republican representative from Utah, did not name any country, saying it was classified information. After the hack there was speculation that it had been done by the Chinese.

Information from the hack was invaluable to other countries because it provided insights into which employees had security clearances, who is dealing with classified information, what vulnerabilities they have and what their fingerprints look like, Chaffetz said.

The report blames the personnel agency for not securing sensitive data despite warnings for years that it was vulnerable to hackers, the Associated Press reported. The hack revealed last year could have been prevented if the agency had basic security controls and recognized from an earlier breach that it was dealing with a sophisticated, persistent enemy, it added.

The OPM has been criticized previously for negligence leading to the hack.

In June 2015 a federal employees union filed a lawsuit against the OPM, its leadership and a contractor, alleging that their negligence led to the data breach.

From at least 2007, the OPM was warned by its Office of Inspector General of significant deficiencies in its cybersecurity protocol, according to the suit filed by the American Federation of Government Employees in the U.S. District Court for the District of Columbia.

According to OPM, in 2015 it discovered two separate but related cybersecurity incidents. The first resulted in the exposure of personnel data of about 4.2 million current and former federal government employees. OPM also discovered malicious cyber activity on its network, resulting in the exposure of background investigation records of about 21.5 million people, who were either current, former or prospective federal employees and contractors.

"Over the past year OPM has worked diligently with its partners across government and made significant progress to strengthen our cybersecurity posture, and reestablish confidence in this agency’s ability to protect data while delivering on our core missions," OPM acting director Beth Cobert wrote in a blog post. The report "does not fully reflect where this agency stands today," she added.